ADDITION OF L-CARNITINE TO ADDITIVE SOLUTION-SUSPENDED RED-CELLS STORED AT 4-DEGREES-C REDUCES IN-VITRO HEMOLYSIS AND IMPROVES IN-VIVO VIABILITY

BACKGROUND: The role of L-carnitine (LC) as the requisite carrier of l ong-chain fatty acids into mitochondria is well established. Human red cells (RBCs), which lack mitochondria, possess a substantial amount o f LC and its esters. In addition, carnitine palmitoyl transferase, an enzyme that catalyzes the reversible transfer of the acyl moiety from acyl-coenzyme A to LC is found in RBCs. It has recently been shown tha t LC and carnitine palmitoyl transferase play a major role in modulati ng the pathway for the turnover of membrane phospholipid fatty acids i n intact human RBCs, and that LC improved the membrane stability of RB Cs subjected to high shear stress. RBC membrane lesions occur during s torage at 4 degrees C; this study investigated whether the addition of LC (5 mM) to a standard RBC preservative solution (AS-3) affected cel lular integrity with 42 days' storage. STUDY DESIGN AND METHODS: A pai red (n = 10) crossover design was used for RBCs stored in AS-3 with an d without LC. Both in vitro RBC properties reflective of metabolic and membrane integrity and in vivo measures of cell viability (24-hour pe rcentage of recovery and circulating lifespan) were measured at the en d of the storage. In addition, the turnover of membrane phospholipid a nd long-chain acylcarnitine fatty acids and the carnitine content of c ontrol and LC-stored RBCs were measured. RESULTS: It was shown that LC was irreversibly taken up by RBCs during storage, with a fourfold inc rease at 42 days. Furthermore, as found by the use of radiolabeled pal mitate, the stored RBCs were capable of generating long-chain acylcarn itine. The uptake of LC during storage was associated with less hemoly sis and higher RBC ATP levels and by a significantly greater in vivo v iability for LC-stored RBCs than for control-stored RBCs: a mean 24-ho ur percentage of recovery of 83.9 +/- 5.0 vs. 80.1 +/- 6.0 percent and a mean lifespan of 96 +/- 11 vs. 86 +/- 14 days, respectively (p<0.05 ). CONCLUSION: A beneficial effect of the addition of LC to RBCs store d at 4 degrees C was evident. This effect may be related to both bioph ysical and metabolic actions on the cell membrane.